| Waste heat recovered
from compressors can be used for heating. |
| The heat generated by air compressors can
be used effectively within a plant for space heating and/or process water
heating. Considerable energy savings result in short payback periods. |
| Process
heating: Heated water is available
from units equipped with water-cooled oil coolers and after-coolers. Generally,
these units can effectively discharge the water at temperatures between
130 degrees F and 160 degrees F. |
| Space
heating is essentially accomplished by ducting the heated cooling
air from the compressor package to an area that requires heating. If ductwork
is used, be careful not to exceed the manufacturer's maximum back-pressure
allowance. When space heating is used in the winter, arrangements should
be made in the ductwork to return some of the heated air to the compressor
room in order to maintain a 60 degrees Fahrenheit room temperature. This
ensures that the air discharged is at comfortable levels. |
| Waste heat recovery is particularly effective
when the primary air compressor package is an oil-cooled rotary-screw type. |
| Estimating the real energy savings in dollars
must include identifying the actual cost of the current source of energy
(natural gas, electric, propane etc.). (See Energy Savings Through Heat
Recovery.) |
|
| Use of flow controllers. |
| Most compressed air systems operate at artificially
high pressures to compensate for flow fluctuations and downstream pressure
drops caused by lack of "real" storage and improperly designed piping systems.
Even if additional compressor capacity is available, the time delay caused
by bringing the necessary compressor(s) on-line would cause unacceptable
pressure drop. |
| Operating at these artificially high pressures
requires up to 25% more compressor capacity than actually needed. This
25% in wasted operating cost can be eliminated by reduced leakage and elimination
of artificial demand. |
| A flow controller separates the supply side
(compressors, dryers and filters) from the demand side (distribution system).
It creates "real" storage within the receiver tank(s) by accumulating compressed
air without delivering it downstream. The air pressure only increases upstream
of the air receiver, while the flow controller delivers the needed flow
downstream at a constant, lower system pressure. This reduces the actual
flow demand by virtually eliminating artificial demand and substantially
reducing leakage. |
| The importance
of maintenance to energy savings. |
Well-Maintained
vs Poorly Maintained Compressor
Effect on Energy Costs
100 hp rotary-screw
package (10 cents kWh; 8,760 hrs.)
Estimated annual
full load power costs = $75,000
| Poorly
Maintained |
|
Well
Maintained |
|
| Dirty oil filter |
-1%
|
Clean oil filter |
|
| Hot running oil |
-2%
|
Cooler running oil |
|
| Mineral oil |
-2%
|
Synthetic oil |
|
| Dirty inlet filter |
-1%
|
Clean inlet filter |
|
| Fouled air/oil separator |
-2%
|
Normal running air/oil separator |
|
| Total
Energy Cost |
$81,000
|
Total
Energy Cost |
$75,000
|
| Potential
Loss |
$6,000
|
Potential
Savings |
$6,000
|
|
|
| Leaks are expensive. Statistics show that
the average system wastes between 25 and 35% to leaks. In a compressed
air system of 1,000 cfm, 30% leaks equals 300 cfm. That translates into
savings of 60 hp or $45,000 annually. |
| A formalized program of leak monitoring and
repair is essential to control costs. As a start, monitor all the flow
needed during off periods. |
| Equip maintenance personnel with proper leak
detection equipment, and train them in how to use it. Establish a routine
for regular leak inspections. Involve both maintenance and production personnel. |
| Establish accountability of air usage as part
of the production expense. Use flow controllers and sequencers to reduce
system pressure and compressed air consumption. |
| A well-maintained compressor not only serves
you better with less downtime and repairs, but will save you electrical
power costs too. |
|
Evaluating
Compressor Efficiency / Cost-justifying
More Efficient Compressors
|
| © Copyright 1998 Maintenance Resources, Inc. |
| Maintenance Resources can be reached by |
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